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Learn about: Green Hydrogen

Tim Collins

As the world moves towards a more sustainable future, one of the most exciting sources of renewable energy is that of green hydrogen. Mooted as the potential fuel of tomorrow for decades it has largely struggled to get off the ground. It took centre stage at the recent COP26 UN Climate Conference with many countries ramping up their efforts, R&D and importantly their investment into green hydrogen technology.

What is “Green hydrogen”?

Simply put, green hydrogen is hydrogen that has been produced from entirely renewable energy. This is in distinction to ‘grey/black’ and ‘blue’ hydrogen which is hydrogen that has been made from brown/black coal or natural gas/steam, respectively.

Not all hydrogen is created equal

Despite being the most abundant and simple element in the universe, hydrogen rarely exists in a gaseous state on Earth and therefore must be extracted from other, more abundant and readily available compound elements. The resulting hydrogen gas from this process “can then be burned or used as a carrier to provide energy.”

Green hydrogen is produced through electrolysis. In this process an electric current is passed through water splitting it into its constituent elements, namely hydrogen and oxygen. Both the hydrogen and oxygen are then captured and stored. When the electricity used to split the water is generated from a renewable energy source like wind turbines or solar panels, the entire process is free of greenhouse gases, thereby rendering the hydrogen ‘green’. The only by-product of green hydrogen production is oxygen which can simply be released into the atmosphere at no detriment to the environment.

Conversely, the most common and cheapest production method is to heat natural gas in the presence of steam and a nickel catalyst. The ensuing reaction breaks up the natural gas into its constituent elements, one of them being the hydrogen, which is then collected for usage. The by-products from this production method include CO, CO2 and other greenhouse gases which are resultingly released into the atmosphere at a great cost to the environment and climate. As the International Energy Agency notes “worldwide hydrogen production is responsible for CO2 emissions equivalent to that of the United Kingdom and Indonesia combined.”

Advantages and uses of hydrogen

The CSIRO’s 2018 Report into green hydrogen outlines its abundance of practical uses:

 ·   Hydrogen fuel cells can power electric cars and trucks

 ·   Hydrogen could play a substantial “role in decarbonizing hard-to-electrify sectors: long-haul trucking, aviation, and heavy manufacturing.”

 ·   Ammonia produced from hydrogen could also be implemented to power shipping vessels.

 ·   Hydrogen can be used as a suitable substitute for natural gas in a domestic setting (i.e. cooking and heating in homes)

 ·   Revolutionise the steel industry, with green replacing fossil fuels in turning iron ore into green steel.

Challenges for the future

The cost of the technology in the production process is a major hurdle. It is suggested that commercialisation of the technology is economically viable once hydrogen can be produced for under $2 per kilogram. Currently, the Federal government estimates that the cost of production is $5/kg compared to the cost of fossil-fuel based hydrogen production which sits at 2.90/kg.

One company at the forefront of lowering production costs is Hysata, who have recently unveiled their “ultra-high efficiency electrolyser”. Current electrolysers (the component that uses electricity to split water into hydrogen and oxygen) are extremely inefficient, with only 75% energy efficiency – meaning that 25% of the energy put in is wasted. Hysata’s electrolyser can produce hydrogen at 95% fuel cell energy efficiency, potentially lowering the cost of production under $2/kg by 2025.

Hydrogen is also difficult to transport owing its extremely low density. As such, it is either required to be cooled to a temperature of -253oC, in order to liquefy it, or it must be compressed at 700 times atmospheric pressure to convert it into its gaseous state. Moreover, transporting hydrogen requires expensive and highly complex infrastructure such as a vast network of dedicated pipelines, and specifically designed low-temperature tanker trucks/ships. Unfortunately, it is also difficult to transport hydrogen through existing networks of natural gas pipelines as hydrogen causes steel to brittle and crack.

Green hydrogen is clearly an exciting prospect and will be of paramount importance in creating a more sustainable future. Whilst there are barriers to implementation, let’s hope that we in Australia continue to be at the forefront of investment and R&D in this rapidly evolving space.

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